Orthodontic brackets typically are small, slotted devices for use during orthodontic treatment. The brackets usually are configured for attachment to front surfaces of teeth, either by directly cementing a bracket to a tooth surface or by bonding the bracket to a metal band that encircles the tooth, though in some instances brackets may be attached to back surfaces of teeth. Slots in the brackets, which may be referred to herein as archwire slots and/or as archwire passages, are disposed horizontally, or generally horizontally, and are configured to receive an archwire. Traditionally, an archwire is a resilient, curved piece of wire that may be bent and/or twisted prior to installation in the bracket slots, with an archwire typically extending through the slots of all of the orthodontic brackets that are attached to a patient's upper or lower teeth. Engagement between the archwire and the brackets creates corrective, or prescriptive, forces that are directed to the teeth by the orthodontic brackets to urge the teeth into a correct, or desired, alignment, or occlusion.
The archwire may be secured in the archwire slot of an orthodontic bracket by a variety of mechanisms, such as depending on the bracket configuration. For example, a “ligating” bracket typically requires a separate fastener, such as a ligature wire or elastic band, which is tied or otherwise positioned around ligating structures, such as tie wings, on the bracket body to secure the archwire in place within the archwire slot of a bracket. A “self-ligating” bracket, on the other hand, typically includes a clamp, gate, or other self-locking mechanism, such as a closeable bracket slot, that allows such a bracket to retain the archwire in the archwire slot without requiring the use of ligatures or other separate fasteners. Ligatures and/or supplemental fasteners or biasing structures also may be used with self-ligating brackets, but they are not required to retain the archwire in the archwire slot.
Regardless of whether the bracket is a self-ligating bracket or whether the bracket requires separate fasteners or ligatures to secure an archwire in the bracket's archwire slot, orthodontic treatment of a patient's teeth typically requires periodic adjustment of the forces that are imparted to the patient's teeth by the installed orthodontic brackets, archwire(s), etc. Adjustments include changing the magnitude and/or direction of the forces that are imparted to the patient's teeth, such as to adjust the degree to which torque, tip, and/or rotational forces are imparted to the patient's teeth to change the angulation, inclination, rotation, height and/or location of the teeth in order to move the teeth toward an optimal occlusion.
As used herein, tipping forces refer to forces applied to the tooth in the mesial-distal direction. Thus, tipping forces may impact angulation. Torsional forces refer to forces applied to the tooth by an archwire that is in torsion within the archwire passage. Thus, torsional forces tend to rotate the tooth in the buccal-lingual or labial-lingual direction and may impact inclination. Rotational forces refer to applied forces that tend to rotate the tooth about its long axis.
Adjustments of some of these forces, including torsional (i.e., torque) forces, typically requires removal of the archwire from the corresponding brackets, along with replacement of the archwire and, in some cases, removal and replacement of one or more brackets. Even with a bracket that permits the applied forces to be adjusted without removal of the bracket from a patient's tooth, fine adjustment of these forces still may be challenging. Thus, there exists a need for improved adjustable-prescription orthodontic brackets.